False information from a cashier staff and wrong product.

My sister bought a Intax Mini 8 Polaroid as a gift for me on our christmas party. She bought it with an extra film and accidentally got the wide film instead of the right one. She's not sure about what she got so she asked the cashier who's serving her at the moment about it and was told that she got the right one and that it would fit the camera that she bought. We already opened the box of film but not the plastic... Just want to know if we could still return it, especially when its the cashier's fault for giving false information. Thank you